1. Field of the Invention
The present invention relates generally to a method for handling error information between a channel unit and a central computer. The channel unit is arranged between the central computer and a peripheral. More specifically, the present invention relates to a method for acquiring error information when a malfunction occurs in a channel unit and for transferring the acquired error information to the central computer via a data bus.
2. Description of the Prior Art
Plural channel units are provided between an input/output (I/O) controller forming part of a central computer and the corresponding peripherals (I/O devices). Each of the channel units carries out buffering (for example) for gathering data at a time when it is not needed so that the data will be available for processing when it is needed.
When a hardware and/or software malfunction is detected within one of plural channel units, it is necessary for the central computer to obtain the error information from the troubled channel unit for error diagnostics.
According to a known technique, in the event that an error is detected within one of the channel units, the I/O controller brings the channel unit into a freeze mode, after which error information is acquired and then transferred to the I/O controller by way of a dedicated channel to the error diagnostics (viz., a scan-channel).
However, in order to transfer the error information to the I/O controller through the scan-channel, it is required that the I/O controller switches the data transfer clocks to the clocks dedicated to the scan-channel. Accordingly, the prior art technique has encountered the problem in that the operation of all of the channel units coupled to the I/O controller must be temporarily stopped during the time duration from the error information transfer to the I/O controller to the completion thereof. In other words, the normal data transfers between the central processor and all the peripherals, are undesirably discontinued for the above-mentioned period of time.